1. Field of the Invention
The present invention generally relates to engineering and management systems for the design of wireless and wired communication systems and, more particularly, to a method for comparing the performance of wireless and wired systems in any environment (e.g., buildings, floors within a building, campuses, within cities, an outdoor setting, etc.) using a three-dimensional (3-D) visualization method.
2. Description of the Prior Art
As communication systems proliferate, radio frequency (RF) coverage within and around buildings, and radio signal penetration into and out of buildings, has become a critical design issue for communications engineers who must design and deploy cellular telephone systems, paging systems, or new wireless technologies such as personal communication systems (PCS), wireless local area networks (WLAN), and local multi-point distribution systems (LMDS). Emerging hand-held appliances will increasingly use wireless access methods, necessitating the need for tools and methods that allow technicians and engineers to rapidly install such wireless infrastructure. Also, the fiber optic and baseband networks needed to carry internet traffic will proliferate rapidly in the future, as well. In addition, RF networks involving micromachinery, RF identification tags, and optical communication links are of increasing interest due to the rapid miniaturization of communication devices and sensors, and the rapid proliferation of fiber optic bandwidth in and around campuses. Designers are frequently requested to determine if a radio transceiver location or base station cell site can provide adequate, reliable service throughout a room, a building, an entire city, a campus, a shopping mall, or any other environment. The costs of in-building and microcellular wireless communication devices are diminishing while the workload for wireless system design engineers and technicians to deploy such systems is increasing sharply. Given these factors, rapid engineering design and deployment methods accompanied by comprehensive system performance visualization and analysis methods are vital to wireless communication system designers.
In addition, recent research efforts by AT&T Laboratories, Brooklyn Polytechnic, and Virginia Tech are described in papers and technical reports entitled: S. Kim, B. J. Guarino, Jr., T. M. Willis III, V. Erceg, S. J. Fortune, R. A. Valenzuela, L. W. Thomas, J. Ling, and J. D. Moore, “Radio Propagation Measurements and Predictions Using Three-dimensional Ray Tracing in Urban Environments at 908 MHZ and 1.9 GHz,” IEEE Transactions on Vehicular Technology, vol. 48, no. 3, May 1999 (hereinafter “Radio Propagation”); L. Piazzi, H. L. Bertoni, “Achievable Accuracy of Site-Specific Path-Loss Predictions in Residential Environments,” IEEE Transactions on Vehicular Technology, vol. 48, no. 3, May 1999 (hereinafter “Site-Specific”); G. Durgin, T. S. Rappaport, H. Xu, “Measurements and Models for Radio Path Loss and Penetration Loss In and Around Homes and Trees at 5.85 GHz,” IEEE Transactions on Communications, vol. 46, no. 11, November 1998; T. S. Rappaport, M. P. Koushik, J. C. Liberti, C. Pendyala, and T. P. Subramanian, “Radio Propagation Prediction Techniques and Computer-Aided Channel Modeling for Embedded Wireless Microsystems,” ARPA Annual Report, MPRG Technical Report MPRG-TR-94-12, Virginia Tech, July 1994; T. S. Rappaport, M. P. Koushik, C. Carter, and M. Ahmed, “Radio Propagation Prediction Techniques and Computer-Aided Channel Modeling for Embedded Wireless Microsystems,” MPRG Technical Report MPRG-TR-95-08, Virginia Tech, July 1994; T. S. Rappaport, M. P. Koushik, M. Ahmed, C. Carter, B. Newhall, and N. Zhang, “Use of Topographic Maps with Building Information to Determine Antenna Placements and GPS Satellite Coverage for Radio Detection and Tracking in Urban Environments,” MPRG Technical Report MPRG-TR-95-14, Virginia Tech, September 1995; T. S. Rappaport, M. P. Koushik, M. Ahmed, C. Carter, B. Newhall, R. Skidmore, and N. Zhang, “Use of Topographic Maps with Building Information to Determine Antenna Placement for Radio Detection and Tracking in Urban Environments,” MPRG Technical Report MPRG-TR-95-19, Virginia Tech, November 1995; and S. Sandhu, M. P. Koushik, and T. S. Rappaport, “Predicted Path Loss for Rosslyn, Va., Second set of predictions for ORD Project on Site Specific Propagation Prediction,” MPRG Technical Report MPRG-TR-95-03, Virginia Tech, March 1995.
The papers and technical reports are illustrative of the state-of-the-art in site-specific radio wave propagation modeling. While most of the above papers describe a comparison of measured versus predicted RF signal coverage and present tabular or two dimensional (2-D) methods for representing and displaying predicted data, they do not report a comprehensive method for visualizing and analyzing wireless system performance. The “Radio Propagation” and “Site-Specific” papers make reference to 3-D modeling, but do not offer novel display methods or graphical techniques to enable a user to visualize signal coverage or interference in 3-D. Furthermore, there do not exist effective methods that allow a wireless communications technician or designer to rapidly display predicted performance values, or to compare, through visualization, differences in predicted performance values between alternate network design concepts within a particular specified environment.
Common to all wireless communication system designs as well as wired network designs is the desire to maximize the performance and reliability of the system while minimizing the deployment costs. Ways to minimize cost include the use of computer aided design tools that manage many aspects of the design process. Such tools also help create methods that enable the engineer or technician to work quickly. Consider a wireless system, for example. Analyzing radio signal coverage and interference is of critical importance for a number of reasons. A design engineer must determine if an environment that is a candidate for a wireless system contains too much noise or interference, or if the existing wireless system will provide sufficient signal power throughout the desired service area. Alternatively, wireless engineers must determine whether local area coverage will be adequately supplemented by existing large scale outdoor wireless systems, or macrocells, or whether indoor wireless transceivers, or picocells, must be added. The placement of these cells is critical from both a cost and performance standpoint. The design engineer must predict how much interference can be expected from other wireless systems and where it will manifest itself within the environment. Prediction methods which are known to the inventors and which are available in the literature provide well accepted methods for computing coverage or interference values for many cases. However, the implementation of such models are generally very crude, and rely on cumbersome spreadsheets, or inefficient operating platforms in research laboratories with little support and little visualization capability. Inevitably, performance measurements must be made in the environment of interest in order to generate the proper prediction models, or to at least verify the chosen prediction models for acceptable accuracy or reliability.
Depending upon the design goals, the performance of a wireless communication system may involve a combination of one or more factors. For example, the total area covered in adequate received signal strength (RSSI), the area covered in adequate data throughput levels, and the number of customers that can be serviced by the system are among the deciding factors used by design engineers in planning the placement of communication equipment comprising the wireless system. Thus, maximizing the performance of a wireless system may involve the complex analysis of multiple, potentially unrelated factors. The ability to display the results of such analysis in a manner easily interpretable by design engineers is invaluable in wireless system deployment. Three dimensional (3-D) visualization of wireless system operating parameters provides the user with rapid assimilation of large data sets and their relation to the physical environment. As wireless systems proliferate, these issues must be resolved quickly, easily, and inexpensively, in a systematic and repeatable manner.
There are many computer aided design (CAD) products on the market that can be used to design a computerized model of an environment. WiSE™ from Lucent Technology, Inc., SignalPro™ from EDX, PLAnet™ by Mobile Systems International, Inc., (later known as Metapath Software International, now part of Marconi, P.L.C.) and TEMS from Ericsson, Wizard by Safco Technologies, Inc. (now part of Agilent Technologies, Inc.), are examples of CAD products developed to aid in the design of wireless communication systems.
Lucent Technology, Inc., offers WiSE™ as a design tool for wireless communication systems. The WiSE system predicts the performance of wireless communication systems based on a computer model of a given environment using a deterministic radio coverage predictive technique known as ray tracing.
EDX offers SignalPro® as a design tool for wireless communication systems. The SignalPro system predicts the performance of wireless communication systems based on a computer model of a given environment using a deterministic RF power predictive technique known as ray tracing.
Mobile Systems International, Inc., (now a part of Marconi, P.L.C.), offers PLAnet™ as a design tool for wireless communication systems. The PLAnet system predicts the performance of macrocellular wireless communication systems based upon a computer model of a given environment using statistical and empirical predictive techniques. Ericsson Radio Quality Information Systems offers TEMS™ as a design and verification tool for wireless communication indoor coverage. The TEMS system predicts the performance of indoor wireless communication systems based on a building map with input base transceiver locations and using empirical radio coverage models.
The above-mentioned design tools have aided wireless system designers by providing facilities for predicting the performance of wireless communication systems and displaying the results in the form of flat, two-dimensional grids of color or flat, two-dimensional contour regions. Such displays, although useful, are limited by their two-dimensional nature in conveying all nuances of the wireless system performance. For example, slight variations in color present in a two-dimensional grid of color, which may represent changes in wireless system performance that need to be accounted for, may be easily overlooked. Furthermore, as wireless systems proliferate, the ability to visually predict and design for coverage and interference is of increasing value.
Common to all communication system designs, regardless of technology, size or scale, is the need for measurement data at some point in the design process. For environments which are candidates for wireless communication systems, it is essential to first conduct a measurement campaign to determine spectral occupancy, noise levels, interference levels, or available channels.
Whether in the initial design stage or the final verification stage, or during ongoing maintenance during the lifecycle of a communication system, no communication system is implemented without the input and use of measurement data. However, measurement acquisition within in-building environments is much more tedious and time consuming than in the macrocellular environment where measurement acquisition is carried out using Global Positioning System data to determine the location of the measurement being taken. Global Positioning System (GPS) data, which so many RF engineers have come to rely upon for outdoor measurement acquisition, is not an option for microcell environments in most cases, and is extremely difficult to use reliably within buildings, due to the clutter and resulting attenuation of the GPS satellite signal levels within urban areas and within manmade structures. While new methods, such as the Qualcomm SnapTrack indoor GPS system may offer long-term promise for in-building location, today's readily available GPS solutions are expensive and are seldom available to engineers or technicians tasked with the deployment, measurement, or optimization of in-building or microcell networks. Therefore, recording real-time measurement data within a building becomes a laborious, time-consuming task involving scratched notes and blueprints and manual data entry which are both expensive and ineffectual in many respects.
In addition to measuring RF signal properties from emitted base transceivers there is also a need to measure data throughput time in computer data networks. Throughput time is the time required to transfer a record or file of known size from one computer to another. In order to standardize the measurement of data throughput time for comparison or verification purposes, files of a set size (e.g., 100K) are used and transferred in packet sizes such as 512 bytes. Similar to RF signal attenuation, data throughput time, and each of a many number of other important network measurement parameters, such as packet latency, bit error rate, packet error rate, and bit rate throughput, is also a function of transmission distance and signal obstruction (e.g. walls, doors, partitions), as well as multipath propagation and the specific radio modem design.
Presently, there are no known effective visualization techniques that allow an engineer or wireless technician to display measurement results or rapidly compare, through visualization, various measurement results of various performance measurements of a particular communication network, or collection of networks, within a particular specified environment over time, frequency, or space. Various signal property measurement acquisition tools and systems have been developed to aid in the design of wireless communication systems such as PenCat™, Walkabout PCS™ and TEMS Light.
LCC International Inc. offers the PenCat™ as a pen-based collection and analysis tool for wireless communication design that runs on a small hand-held tablet computer. The PenCat™ system enables a user to roam about a building, take signal property measurement data at a location in the building using a receiver linked to the tablet computer, and link the measured data to that building location on a computer map representing the building by tapping the appropriate portion of the map on the computer screen with a stylus pen. The building map can be entered into the PenCat™ system by either scanning blueprints, sketching the building within the application, or importing from another source. PenCAT uses two dimensional bit maps to model the building environment. Safco Technologies, Inc. (now part of Agilent Technologies, Inc.) offers the Walkabout PCS™ system as a portable survey coverage system for use in indoor or outdoor wireless communication system design. Similar to PenCat™, the Walkabout PCS™ system utilizes a hand-held computer linked to a receiver for measuring signal properties at a given location and linking the measured property data to that location represented on a stored computer map. Also similar to the Safco Walkabout is the Agilent 74XX indoor measurement system, which also uses a bitmap floor plan. Ericsson Radio Quality Information Systems offers the TEMS Light system as a verification tool for wireless communication indoor coverage. The TEMS Light system utilizes a Windows-based graphical interface with two dimensional bit map drawings on a mobile computer linked to a receiver to allow a user to view a stored building map, make location specific data measurements, and link the measured data to the represented location on the stored computer map. Unlike other in-building communication measurement systems, InFielder™ by Wireless Valley Communications, Inc. merges measurement data with periodic updates of position location on a three-dimensional model of the physical environment. The InFielder™ product concept is disclosed in U.S. patent application Ser. No. 09/221,985 filed Dec. 29, 1998, and the contents of this application are herein incorporated by reference. However, as originally disclosed in the aforementioned patent application, InFielder, does not offer an efficient method for rapidly viewing and comparing measurement data in a 3-D environment such that measurement values, and comparisons of measurement values, may be quickly determined and inferred by the user.